Oleg,

There is a "fall arrest" mechanism, which is nothing but sort of an automatic emergency brake. Absolutely mechanical in action, no electronic controls involved.

What it does, it only actuates when speed while up or down exceeds a preset value (probably tension in a spring). When it actuates it siezes the rollers on the rail and stops. It does not regulate the speed. It is reset only manually to allow the maintenance crew to look at the problem and passengers be rescued.

All modern age elevators have this fall arrest system. Although an old invention.

The electronics has been excluded from it only to provide 100% surety in it to work.

You left the machine drive open for others to be filled out:

The most preferable drive is the pully and belt type because it provides a slip. If the lift gets stuck say due to emergency brake or some mechanical latch then the motor won't get much overloaded.

The gears drives are not preferred here. Although any drive can be used with "Electronics looking at everything" but what if electronics fails when system fails. Therefore the system has to be mechanically fail safe.

The Door safety:

The IR is to only let somebody in, who decided just in time to get in.
Even if IR fails and person gets between the door panels the lift won't move as a mechanically actuated switch is not pushed which only by the meeting of the two door panels.


Good discussion while waiting for details of the actual question.

Simon you out there .... come on pal speak up something.

Babar/